Crematoriums run at ~1600 degrees F(871)°C. It takes roughly 2.5 hours to burn off organic matter (still leaving behind bones and teeth that then must be crushed in a separate process).
Heat Energy (calories) = m * c * ΔT m = mass of human ( average: 80.7 kg )
c = specific heat of human body ( 3470 J. kg-1 . K-1 )
ΔT = Change in temperature. ( cremation temp - room temp )
Room Temperature = 26 °C
1600 °F = 871°C
So: H.E. = 80.7kg * 3470 J/kg*k * (871-26)
H.E. = 236624.5 kcal
The energy in a kg of coke(coal) is 8000 kcal/kg. So one body would (under IDEAL conditions) take 236625kcal/8000kcal/kg = 29.57 or about 30kg (66 pounds!) of fuel to burn.
To cremate say 3-6 million hebrews, therefore, it would take around 100,000-200,000 metric tons (220,462,280-440,924,560 pounds!) of coal.
That is an awful lot of coal (i.e. impossible) for a country that couldn’t heat its homes, operate its tanks or fly it's aircraft etc. because of beyond-critical fuel shortages.
Also when coal is burnt, it generates around 5-10% of its weight in ash. So, I'll be generous and say 5%. So 9 million kg of ash from the fuel. The average adult leaves ~2.5kg of bone fragments, teeth and ash from cremation. So we have 9 million + 2.5x6million = 24 million kg of ash.

De zes miljoen koekjes fabriek.
De meest geavanceerde koekjes oven kan 1000kg/hr bakken.
Gemiddeld gewicht koekje: 62kg
1000 : 62 = 16,12 koekjes/uur
16.12 × 24 = 386.88 koekjes per dag
386.88 × 365 = 141,211.2 koekjes per jaar
6.000.000 ÷ 141211.2 = 42.48 Jaar voor zes miljoen koekjes.